LEAP#191 glowing LEDs on 1.5V
So for another project I wanted some "glowing" LEDs, ideally powered from a single 1.5V AA or AAA battery. That seemed like an interesting challenge, especially when the forward voltage of the LEDs I'm using is about 2.1V.
I had a feeling I could cobble together a couple of ideas (Relaxation Joule Thief and RC Oscillator) .. and lo, it works!
As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.
Here's a glimpse of the "modified oscillation". CH2 (red) is the LED cathode/transistor collector - as it rises and falls the LED slowly switches off then back on.
For protoboard-based builds I tend to layout the schematic with PAD tools (Pencil-Aided Design) ...
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LEAP#137 Toroidal Joule Thief
In #129 I posted about a two-transistor boost circuit. This is an even simpler circuit - very common over around the internet and known as the archetypal "joule thief". The smallest I've seen is Eric Wasatonic's micro version.
I stuffed my circuit into a AA battery holder and it works great as a night light, powered by either a single somewhat-depleted AA or AAA battery.
As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.
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LEAP#129 Relaxation Joule Thief
I was inspired by w2aew's excellent video to check out the Ears To Our World humanlight project. It's a good cause, although shipping costs kill the idea of buying one myself - better just to make a direct donation.
It's also an interesting circuit - a variation on the many "joule thief" circuits out there - and also demonstrates some of the basics that under-pin boost converter power supplies.
As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.
With my particular mix of components, I'm getting almost 40% duty cycle which actually produces an apparently very bright LED on just 1.5V supply.
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LEAP#001 basics of 7-segment LED control
Going back to basics - this project is a test of directly driving a common cathode 7-segment LED with an Arduino. It covers the fundamentals behind more advanced circuits like this custom PCB with register interface.
As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.
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